How to boot with iscsi in UEFI env?

[scan80269]

On my system acting as iSCSI disk server (running Windows Server 2012 R2/2016/2019 OS - with iSCSI Target Server feature enabled) I set up Tiny PXE Server to load ipxe-snponly-x86-64.efi (64-bit UEFI iPXE) for UEFI clients network booting via PXE. Once a client boots to iPXE, my iPXE script launches sanboot of an iSCSI virtual disk based on Ethernet MAC address match to initiate Win10 OS boot. The iSCSI virtual disk for the client is set up with GPT style disk partitions to properly support Win10 booting in UEFI mode (a Win10 requirement by Microsoft).

My iPXE script is set up such that sanboot of a virtual disk will fail if it doesn't have Win10 properly installed, in which case the script will continue onto launching wimboot to boot the client into WinPE in preparation for over-the-network Win10 OS installation into the iSCSI virtual disk dedicated to that client. I created a small (10GB) iSCSI virtual disk to carry the Win10 OS installation files, to avoid having to plug a USB flash drive into the client.

On many modern PCs, in order for UEFI PXE to work, "legacy" support (a.k.a. CSM - Compatibility Support Module) needs to be disabled in BIOS setup.

Once you can get a UEFI client to chain boot from PXE to iPXE, the rest, such as using sanboot to boot Win10 should be relatively straightforward.